| Abstrakt: |
The transmission of sound through pipe walls is an important component of the problem of determining the noise generated by valves. In this paper we present a progress report on an experimental program to determine the transmission loss (TL) of a series of pipes, as a function of flow within the pipe. The experimental program is outlined, and the results of measurements on a 6-in.-diam., schedule 40 (0.29-in. wall thickness) pipe are discussed in detail. The experimental data for this pipe indicate three different frequency regimes, where different processes controlled the TL. At low frequency (below ka ≈ 3), the TL shows a -12 to -18 dB per octave slope, and is relatively unaffected by flow. Between this frequency and the ring frequency (∼10 kHz), the TL is roughly independent of frequency, but is strongly affected by flow. (TL in this frequency range decreased by approximately 10 dB with a flow change from 0 to 400 ft/sec.) Above the ring frequency, the TL exhibited a 3 to 6 dB per octave slope, and a less strong flow dependence. These data are then compared with theoretical TL estimates by Cremer, Heckl, and Morfey. [;Work supported by Westinghouse Corporation, Steam Turbine Division, Lester, Pennsylvania.] [ABSTRACT FROM AUTHOR] |
